Kepler-731 b
Astrophysical Synthesis & Habitability Characterization
Kepler-731 b is a confirmed gas giant exoplanet orbiting the star Kepler-731, located approximately 4100.3 light-years (1257.16 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 1.4411% across the stellar disk), this world has a measured radius of 13.88 Earth radii (1.24 R♃), though radial-velocity mass constraints remain unmeasured in the current composite catalogue.
In its orbital architecture around Kepler-731, Kepler-731 b completes one full revolution every 3.856 Earth days at a semi-major axis of 0.0505 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 142.5 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1212 K (+939°C / +1722°F) and receiving 456.70 S⊕ (~621,573 W/m²), Kepler-731 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-731 is classified as a stellar host with an effective photospheric temperature of 5,849 K, a radius of 1.06 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 1.18 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.8 Gyr and a metallicity of [Fe/H] = 0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-731 shines at apparent V-band magnitude 15.386 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-731 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,849 K |
| Stellar Radius | 1.0600 R☉ |
| Stellar Mass | 1.0300 M☉ |
| Bolometric Luminosity | 1.18 L☉ |
| Metallicity [Fe/H] | 0.040 dex |
| Stellar Age | 3.800 Gyr |
| Apparent Magnitude | V: 15.386 · G: 15.285 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.050500 AU |
| Orbital Period | 3.856 days |
| Mean Orbital Velocity | 142.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.9600° |
| Insolation Flux | 456.7030 S⊕ (~621,573 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4100.300 LY (1257.160 pc) |